Catalan Police arrested two men earlier today in connection with the incident, and two other suspects were killed in a shootout with officers.

It is also not currently known how many attackers were involved. Isis claimed responsibility for the attack.

One of the suspects was named by police as Driss Oukabir. However, it has since been claimed that he handed himself into police after seeing his face in the media.

Oukabir claims he was 106km away in Girona at the time of the attack, and that his documentation – which was used to rent the van – was stolen.

Horrific footage shot from overhead showed terrified pedestrians screaming as they ran away from the scene, while others taken in the aftermath show at least 19 people lying on the floor covered in blood.

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Armed police officers patrol an empty street, after a van crashed into pedestrians near the Las Ramblas avenue in central Barcelona (Picture: Reuters)

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Catalan emergency services said people should not go to the area around Plaça Catalunya, and should stay away from the centre of Barcelona.

Mr Anwar described the scene as ‘chaos’, with everyone in ‘panic mode’.

He added: ‘Police officers who got there just started screaming at people to move back, move back.

‘One of the shopkeepers tried to speak to him. He said he saw five or six people seriously injured on the ground, a van had driven into people.

‘And literally within probably 30 seconds, police vans, ambulances, police officers with guns, were piling out and we were being sectioned off and then being pushed rapidly back down Ramblas.’

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(Picture: AFP/Getty)

A police officer cordon off a street in Barcelona (Picture: AP)

People were seen screaming as they ran away from Las Ramblas (Picture: EPA)

People are being urged to get out of the centre of Barcelona (Picture: EPA)

Will Ako, 26, from London, was eating in a restaurant called Taller De Tapas with his family when they heard a disturbance.

He told the Press Association: ‘We had just finished eating and were about to leave when we heard a commotion and the patrons in the restaurant rushing from their seats.

‘I then saw people running to the east of the restaurant and I saw a couple of people about 30 yards down the road crouching around what looked like someone on the ground and they were calling for assistance.

‘Within a couple of minutes, police started to arrive and they were running west of the restaurant and some were telling us to stay inside.

‘Soon after, loads of cars, bikes and ambulances arrived and then the armed police.’

He said he was in the restaurant with around 40 people, adding: ‘We’re not sure what’s happening.’

(Picture: PA)

Police ordering people to leave the scene (Picture: AP)

Another Barcelona eyewitness told LBC: ‘I saw white van driving at 80-100kmph as it drove into groups of people.’

Brendon Sissing is in Las Ramblas and said he saw ‘people screaming and people being knocked down by this van’.

‘It knocked a whole bunch of people and just kept on going,’ he said.

Tom Gueller, who lives on an adjoining road, was forced to flee the scene when he saw the van hurtling through the crowds.

He told BBC’s PM: ‘I heard screams and a bit of a crash and then I just saw the crowd parting and this van going full pelt down the middle of the Ramblas and I immediately knew that it was a terrorist attack or something like that.

‘I ran away, I mean I live near, I had to run back about 50 metres or so and go up to my flat and obviously see what’s happening on the road from my balcony.’

Asked about the van, he said: ‘It wasn’t slowing down at all. It was just going straight through the middle of the crowds in the middle of the Ramblas.’

Mr Gueller said many of the shops had pulled their shutters down and armed police were positioned on street corners, with cordons in place on the road.

Two people have reportedly been killed in the attack (Picture: EPA)

Spanish Prime Minister Mariano Rajoy said on Thursday he was in contact with authorities after a van mowed down dozens of people in Barcleona’s city centre.

Rajoy said on Twitter the priority was to attend to the injured.

Las Ramblas, a street of stalls and shops that cuts through the center of Barcelona, is one of the city’s top tourist destinations. People walk down a wide, pedestrianized path in the center of the street, but cars can travel on either side.

Simon Manley, the British ambassador to Spain, said the Foreign Office was ‘in contact with the authorities and seeking further information following the incident’.

A Foreign Office spokesman said: ‘We are in contact with the Spanish authorities and seeking more information following an incident in Barcelona. Anyone in the area should follow the advice of the emergency services.’

My thoughts are with the victims of this barbaric terrorist attack in the great city of Barcelona and with their brave emergency services.

Former US president Barack Obama also offered his condolences on Twitter, writing: ‘Michelle and I are thinking of the victims and their families in Barcelona. Americans will always stand with our Spanish friends.’

He then signed off with ‘un abrazo’ – which is a Spanish sign-off meaning ‘a hug’.

Michelle and I are thinking of the victims and their families in Barcelona. Americans will always stand with our Spanish friends. Un abrazo.